Field of the Invention
The present invention relates in general to the field of retrofitted hydraulic/pneumatic clutches and power take-offs “PTOs”. The terms hydraulic and pneumatic are used interchangeable and are intended to mean pressurized fluids in general, for example, pressurized hydraulic oil or compressed air.
Discussion of the Related Art
A power take-off or power takeoff (PTO) is any of several apparatus and methods for taking power from a power source, such as a running engine, and transmitting it to an application such as an attached implement, or separate machines. Most commonly, it is a system comprising a flywheel of an engine, which may be in a vehicle or another tool, can be easily connected and disconnected to a corresponding input shaft on the application end. The power take-off allows implements to draw energy from the engine. Semi-permanently mounted power take-offs can also be found on industrial and marine engines, for example. These applications typically use a drive shaft and bolted joint to transmit power to a secondary implement or accessory. In the case of a marine application, such shafts may be used to power pumps.
Commonly used PTOs use a hand lever that is manually pivoted to engage and disengage a clutch that transfers rotary motion from the PTO to the machine (such as a pump). The hand lever is typically attached directly to a bell housing that protects the clutch assembly within the PTO. In order to actuate the clutch, an operator must be located next to the bell housing which means the operator cannot operate the vehicle or tool equipped with the PTO, as the operator must be present by the bell housing.
Known hydraulically actuated clutches and PTOs use a rotary union, or collector, and drilled shafts to route oil/air to a rotating piston/cylinder. These devices require a large portion of the entire clutch actuation assembly to be replaced with a costly substitute. They also require larger cylinder areas that use lower pressure through the rotary union or collector. Such systems must maintain the applied pressure in order to keep the clutch engaged which generates heat and wear on multiple components, thus, reducing system efficiency.
Hydraulic actuators have also been introduced to remotely actuate the clutch allowing the operator to remain in a driver seat or cabin of the vehicle or any other remote location. While this addressed one problem, it introduced new problems. The mechanical linkage assembly is typically completely replaced with a hydraulic assembly. This introduces a significant cost and also a complicated retrofit procedure. Also, due to the nature of the hydraulic operation, hydraulic pressure is required at all times during clutch engagement in order to operate the PTO machine (e.g., a pump).
In one example, a hydraulic PTO clutch works by first pressurizing the cylinder. This forces the piston to clamp and lock the friction and steel clutch discs. When pressure is removed, the steel clutch disks and clutch friction disks, with the use of springs within the clutch pressure plate for example, thus, disengaging the clutch pressure plate from the clutch. When there is no pressure applied to the cylinder, there is a clearance maintained between the friction and steel clutch pressure plate disks. As a result, consistent pressurization of the cylinder and engagement of the piston is required for the clutch to remain actuated. The constant hydraulic force present increases the wear of the hydraulic parts as the forces are present for the whole duration of work required by the application.
What was therefore needed is a hydraulic PTO clutch actuation device that only requires hydraulic pressure during engagement and disengagement. What also needed is a hydraulic PTO clutch that remains engaged without constant hydraulic pressure. What additionally desired is a hydraulic PTO clutch that retains the mechanical linkage to avoid costly replacement parts and increased labor.